The use of cathode ray tube based instruments, such as oscilloscopes, to analyze internal combustion engine performance, has become prevalent in recent years. The increased use of these instruments is in part due to the increasing complexity of the electronic portions of internal combustion engines and in part due to the increasing technical abilities of the persons performing the analyses. Uses for these instruments in analyzing internal combustion engines range from monitoring the timing of the electrical and mechanical functions of the engine relating to the coincidence of spark discharge and cylinder operation to measuring the multitude of electrical signals present in the modern internal combustion engine.
Proper use of an oscilloscope requires that the horizontal sweep be synchronized with the operation of the device being tested. With regard to internal combustion engines, current methods generally utilize an inductive device to pick up the spark discharge of a reference cylinder. When a spark discharge is detected, the inductive pick-up device produces a signal that triggers the horizontal sweep of the oscilloscope. This method of triggering the horizontal sweep of an oscilloscope has a major disadvantage. Specifically, during a horizontal sweep, an auto engine analyzer is designed to display signals derived from each cylinder in timed sequence on the oscilloscope. For example, a spark discharge signal for each cylinder generated during a cycle of engine operation may be displayed side by side. If the triggered sweep of the oscilloscope and the spark discharge of the reference cylinder occur at the same time, the reference cylinder spark discharge signal will not be properly displayed in relation to other cylinders of the engine under test. As a matter of fact, the beginning portion of the reference cylinder spark discharge signal may not be displayed at all.
As will be readily appreciated from the foregoing discussion, there is a need for a trigger generator for synchronizing the horizontal sweep of a cathode ray tube based instrument that will provide a more effective trigger signal than that derived from a reference cylinder spark discharge.